The head of Russian military intelligence, which is accused of orchestrating the Salisbury Novichok attack, has died. Igor Korobov died on Wednesday after "a serious and long illness," Russian news agencies reported, citing the defence ministry. The 63-year-old GRU Chief's death comes after a series of embarrassments for the secretive organisation, for which he was reportedly berated by President Vladimir Putin. Mr Putin reportedly gave Mr Korobov a personal dressing down last month for the bungled operation to poison former Russian spy Sergei Skripal and his daughter. Russian journalist Sergey Kanev, who writes for an investigative group funded by Putin foe and former oligarch Mikhail Khodorkovsky, reported that Mr Korobov fell ill after the meeting with Mr Putin. Evgeny Buzhinsky, a former Russian general, dismissed allegations of foul play. Commenting on suggestions that Mr Korobov's death was untimely, he told the BBC: "No you are completely wrong. It was a long, long struggle against a very bad disease ... In Russia no one is suspicious, believe me." The defence ministry called General Korobov, who ran the spy agency since 2016, "a wonderful person, a faithful son of Russia and a patriot of his homeland." It did not give further details about his death. Gen Korobov had worked in military intelligence since 1985. In 2016, Mr Putin made him head of the Main Directorate of the General Staff of the Russian Armed Forces - also known as the GRU. He took over from Gen Igor Sergun, who died of a heart attack at the age of the 58. Michael Carpenter, a Russia adviser for Barack Obama's administration, tweeted on Thursday: "His predecessor died in 2016 of a heart attack. Life expectancy for incumbents of this job is pretty low, but then so is the median life expectancy in Russia." At a glance | GRU Gen Korobov was sanctioned along with other GRU officers by the United States for activities that "undermine cybersecurity on behalf of the Russian government." The West has blamed the GRU for a string of brazen attacks. Britain has accused it of attempting to poison Mr Skripal and his daughter with a nerve agent in the English city of Salisbury. The botched assassination attempt led to the death of Dawn Sturgess, who, along with partner Charlie Rowley, fell ill after handling a container contaminated with the nerve agent in June. The Netherlands believes the agency has tried to hack the global chemical weapons watchdog, and US intelligence agencies said GRU was behind attempts to hack the 2016 US presidential election. Russia denies all the allegations. But the GRU has also suffered humiliation after the UK revealed the identities of the suspects behind the Skripal poisonings. The agents accused of carrying out the poisoning were named as Alexander Mishkin and Anatoly Chepiga, Dutch and British authorities also exposed the identities of the four Russian GRU operators who took part in the bungled operation to hack the headquarters of the Organisation for the Prohibition of Chemical Weapons (OPCW). Four GRU operatives were caught trying to hack into the Organisation for the Prohibition of Chemical Weapons after Salisbury Credit: Ministerie van Defensie The four Russian spies had in their possession laptops and mobile phones holding damning proof of the cyber hacking operations of its notorious Unit 26165, also known as “GRU 85 Main Special Service Center”. One of them even had a taxi receipt showing he had been picked up from the rear entrance of Unit 26165’s headquarters when he went to the airport. There was fresh embarrassment when further database research revealed 305 other individuals thought to be working for the Russian intelligence agency. At the time, Bob Seely, the Tory MP who sits on the Foreign Affairs Committee, described the lapses that led to the identity of the GRU spies being exposed as "extraordinarily unprofessional". "It shows that subversion is probably beyond their professional capability - they can't even cover their tracks in the most basic of ways. It is very sloppy and makes President Putin look foolish," he added. The GRU has been at the forefront of several of the most controversial Russian intelligence operations in recent years. As well as the brazen hacks, its agents were accused of a failed attempt to mount a coup in Montenegro in 2016, and its special forces are deeply involved in Russia's semi-covert wars in Ukraine and Syria.